HVAC controller having keypad input and method of operation thereof

ABSTRACT

A heating, ventilation and air conditioning (HVAC) controller, a method of receiving signals from a keypad and an HVAC system incorporating the controller or the method. In one embodiment, the HVAC controller includes: (1) a keypad having at least first and second banks, (2) a reference signal source configured to generate a time-varying untransformed reference signal and provide the untransformed reference signal to the first bank, (3) transformation circuitry configured to transform the untransformed reference signal into a transformed reference signal and provide the transformed reference signal to the second bank and (4) a processor having interrupt pins coupled to corresponding keys of both the first and second banks and a further interrupt pin coupled to receive one of the untransformed and transformed reference signal.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/692,335, filed on Apr. 21, 2015. U.S. patent application Ser. No.14/692,335 claims the benefit of U.S. Provisional Application No.62/000,353, filed on May 19, 2014. U.S. patent application No.14/692,335 and U.S. Provisional Patent Application No. 62/000,353 areincorporated herein by reference.

TECHNICAL FIELD

This application is directed, in general, to heating, ventilation andair conditioning (HVAC) controllers and, more specifically, to an HVACcontroller in which input signals from a keypad are received and actedupon.

BACKGROUND

A heating, ventilation and air conditioning (HVAC) system commonlyemploys a controller for governing the operation of at least some partof the HVAC system. For example, a rooftop unit (RTU), which is mostoften used to condition a commercial building, may employ a controllerto activate a compressor or a furnace to cool or warm air and a blowerto deliver the cool or warm air to the building beneath. A controllerproduces one or more output (control) signals based upon one or moreinput (sense) signals.

Controllers often include a keypad configured to allow a person, such asa technician or installer, to configure, diagnose or control theoperation of the HVAC system. The keypad has multiple keys (or,synonymously, buttons), typically arranged in a two-dimensional array ofcolumns and rows, that generate input signals to the controller whendepressed. In a typical keypad, each key produces a unique input signal.

The keypad is merely an input device; other circuitry must be providedto receive and act on the input signals the keypad provides. In the caseof an HVAC controller, the controller's processor is configured toperform this function. Two conventional alternative approaches may beused to couple a keypad to a processor. A first approach is to coupleeach address line representing each column and row of the keypad to adifferent input pin of the processor. For example, a keypad having threecolumns and four rows would use 3+4=7 input pins. The pressing of a keymanifests as a change of state in the two address lines corresponding tothe column and row in which the key lies, The processor continuallyscans (or, synonymously, polls) the pins to detect whether the states ofany of the address lines have changed, thereby indicating the occurrenceof a keystroke and identifying the particular key pressed. A secondapproach to couple a keypad to a processor is to couple a linecorresponding to each key to a different input pin of the processor. Forexample, a keypad having three columns and four rows would use 3×4=12input pins. As with the first approach, the processor continually scansthe pins to detect whether the state of any of the lines has changed,thereby indicating the occurrence of a keystroke and identifying theparticular key pressed.

Unfortunately, both approaches have shortcomings. The scanning requiredby the first approach is relatively complex, consumes significantprocessing resources (“bandwidth”) and ultimately increases the overallcost and power consumption of the controller. The second approachrequires substantially less and simpler scanning. Unfortunately, itrequires more pins than the first approach, which typically increasesthe overall cost and complexity of the controller. Nevertheless, bothapproaches are commonly employed in commercially available HVACcontrollers.

SUMMARY

One aspect provides an HVAC controller. In one embodiment, the HVACcontroller includes: (1) a keypad having at least first and secondbanks, (2) a reference signal source configured to generate atime-varying untransformed reference signal and provide theuntransformed reference signal to the first bank, (3) transformationcircuitry configured to transform the untransformed reference signalinto a transformed reference signal and provide the transformedreference signal to the second bank and (4) a processor having interruptpins coupled to corresponding keys of both the first and second banksand a further interrupt pin coupled to receive one of the untransformedand transformed reference signal.

Another aspect provides a method of receiving signals from a keypad. Inone embodiment, the method includes: (1) providing one of anuntransformed and a transformed time-varying reference signal to aninput pin of a processor, (2) providing the untransformed referencesignal to an interrupt pin of the processor when a key in a first bankis pressed, (3) providing the transformed reference signal to theinterrupt pin when a key in a second bank is pressed and (4) in responseto assertion of an interrupt on the interrupt pin, comparing states ofthe input and interrupt pins to determine which of the key in the firstbank and the key in the second bank asserted the interrupt.

Yet another aspect provides an HVAC system. In one embodiment, the HVACsystem includes: (1) a compressor, (2) a furnace associated with thecompressor, (3) a blower associated with the compressor and furnace and(4) a controller associated with the compressor, the furnace and theblower, the controller having: (4a) a keypad having at least first andsecond banks, (4b) a reference signal source configured to generate atime-varying untransformed reference signal and provide theuntransformed reference signal to the first bank, (4c) transformationcircuitry configured to transform the untransformed reference signalinto a transformed reference signal and provide the transformedreference signal to the second bank and (4d) a processor havinginterrupt pins coupled to corresponding keys of both the first andsecond banks and a further interrupt pin coupled to receive one of theuntransformed and transformed reference signal.

BRIEF DESCRIPTION

Reference is now made to the following descriptions taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a high-level block diagram of an HVAC system and a controllertherefor;

FIG. 2 is a block diagram of a portion of one embodiment of thecontroller of FIG. 1 showing, in particular, keypad input thereto; and

FIG. 3 is a flow diagram of one embodiment of a method of receivingsignals from a keypad.

DETAILED DESCRIPTION

As stated above, while both approaches described in the Background aboveare commonly employed in commercially available HVAC controllers, theyeach have shortcomings that ultimately diminish the controller'sperformance. These shortcomings grow as the number of keys in the keypadincreases. It is realized herein that an approach that requires lessthan one processor pin per key and reduces scanning may reduce the powerconsumption, complexity and cost of an HVAC controller.

It is further realized herein that multiple keys can be associated witha given processor pin, as long as some mechanism exists to tell whichkey is being pressed. It is further realized that a time-varyingreference signal and circuitry for transforming (e.g., phase-shifting orinverting the reference signal) may be employed to provide the mechanismto tell which key is being pressed. It is yet further realized thatinterrupt pins can be used to reduce, and perhaps eliminate scanning todetect whether a key has been pressed. Those skilled in the pertinentart understand that interrupt pins are a special type of input pin that,when “asserted” (brought to a logic high value) interrupts the normalexecution of software or firmware instructions in the processor andprompts the execution of special software or firmware instructions,often called an “interrupt handler.”

Described herein are various embodiments of a controller having keypadinput and a method of receiving signals from a keypad. Before describingthe embodiments in detail, an example of an overall HVAC system havingsuch controller or employing such method will be described.

FIG. 1 is a high-level block diagram of an HVAC system 110 and acontroller 120 therefor. The HVAC system 110 includes a thermostat 111,a compressor 112, a furnace 113 and a blower 114, which are associatedwith each other in that ones of them are coupled to and cooperate withone another. The thermostat 111 is configured to generate commands tocool, warm and/or move air through the HVAC system, typically as afunction of the relationship between a sensed indoor temperature and aset point temperature. The compressor 112 is configured to compress andpropel a refrigerant through a loop to transfer heat between evaporatorand condenser coils (not shown) to cool air passing through theevaporator coils. The furnace 113 is configured to heat air either bygas combustion or electrical resistance. The blower 114 is configured topull air from a conditioned space (e.g., a building interior), throughthe evaporator coils and/or furnace 113 and reintroduce the air backinto the conditioned space.

Those skilled in the pertinent art will understand that HVAC systems maytake many alternative forms. For example, some HVAC systems havedehumidifiers, while others have heat pumps that operate in conjunctionwith or in lieu of the compressor 112 and furnace 113. Still others havemultiple compressors or multi-stage compressors. Yet others havemultiple furnaces and/or multiple blowers, dampers or other equipment.Though “HVAC” implies that the HVAC system is capable of both coolingand heating air, the term is used generically to encompass systems thateither cool or heat air and even those that only ventilate air by meansof a blower without either cooling or heating the air. Further, theinvention is not limited to a particular type, size or configuration ofHVAC system.

The controller 120 includes a keypad 121, a processor 122 and a display124. The processor 122 is configured to execute software or firmwareinstructions to carry out computations and logical operations thattypically constitute a useful process. In the embodiment of FIG. 1, theprocessor 122 is configured to control the HVAC system 110 based onvarious input signals and one or more control algorithms. Variousunreferenced arrows in FIG. 1 leading from the thermostat 111, thecompressor 112, the furnace 113 and the blower 114 to the front-endcircuitry 121, then to the processor 122 then back to the compressor112, the furnace 113 and the blower 114 illustrate one embodiment of acontrol flow involving the HVAC system 110 and the controller 120. Theprocessor 122 may be of any conventional or later-developed type,including: a microcontroller, a microprocessor, a digital signalprocessor and a programmable gate array. Other processor types may beemployed in still other embodiments.

The keypad 121 is an input device having multiple depressible keys,buttons or areas of a touch-sensitive display configured to generateinput signals for the processor 122. The keypad 123 may allow, forexample, a service technician to program, configure, diagnose or changethe operation of the HVAC system 110 or controller 120. In theillustrated embodiment, the keypad 121 has multiple, momentary-contactkeys arranged in a two-dimensional array of columns and rows. Thedisplay 123 is an output device that the processor 122 can drive todisplay text, images or a combination of both. In the illustratedembodiment, the display 124 is a liquid crystal display. In analternative embodiment, the display 124 is of another conventional orlater-developed type.

FIG. 2 is a block diagram of a portion of one embodiment of thecontroller of FIG. 1 showing, in particular, keypad input thereto. FIG.2 shows the keypad 121 and processor 122 of FIG. 1. The keypad 121 ofFIG. 2 happens to have 12 keys. FIG. 2 shows various keys 211 a, 211 b,211 c, 211 d, 211 e, 211 f, 212 a, 212 b, 212 c, 212 d, 212 e, 212 farranged or divided as shown into a first bank 211 and a second bank212. The keys 211 a, 212 a correspond to one another and are coupled toa first interrupt pin 224 a of the processor 122. The keys 211 b, 212 bcorrespond to one another and are coupled to a second interrupt pin 224b of the processor 122. The keys 211 c, 212 c correspond to one anotherand are coupled to a third interrupt pin 224 c of the processor 122. Thekeys 211 d, 212 d correspond to one another and are coupled to a fourthinterrupt pin 224 d of the processor 122. The keys 211 e, 212 ecorrespond to one another and are coupled to a fifth interrupt pin 224 eof the processor 122. The keys 211 f, 212 f correspond to one anotherand are coupled to a sixth interrupt pin 224 f of the processor 122.

A reference signal source 230 is configured to generate a time-varyinguntransformed reference signal. In the illustrated embodiment, thetime-varying untransformed reference signal is periodic (i.e. a clocksignal). In an alternative embodiment, the time-varying untransformedreference signal is aperiodic. In the illustrated embodiment, thetime-varying untransformed reference signal varies between zero voltsand a digital logic voltage (e.g., 5 volts or 3.3 volts) typicallyselected to be compatible with the operating voltage of the processor122. In another embodiment, the time-varying untransformed referencesignal varies between other extremes. In the illustrated embodiment, thetime-varying untransformed reference signal is a square wave. In analternative embodiment, the time-varying untransformed reference signalis a sine or triangular wave.

Transformation circuitry 240 is configured to transform theuntransformed reference signal into a transformed reference signal. Theuntransformed reference signal is provided to the first bank 211, andthe transformed reference signal is provided to the second bank 212. Inthe embodiment of FIG. 2, the untransformed reference signal is alsoprovided to an input pin 223 of the processor 122. In the illustratedembodiment, the transformation circuitry 240 transforms the referencesignal by inverting it and includes first and second inverters 241, 242configured to invert and re-invert the untransformed reference signal toyield the transformed and untransformed reference signals. Because thereference signal of FIG. 1 is periodic, inversion is the same as a180.degree. phase shift. Again, the untransformed reference signal(emerging from the inverter 242) is provided to the first bank 211 andthe input pin 223, and the transformed reference signal (emerging fromthe inverter 241) is provided to the second bank 212.

The operation of the illustrated keypad input will now be described.With no keys being pressed, the processor executes instructions in anormal manner. When a key is pressed, e.g., the key 212 a, thetransformed reference signal is provided to the first interrupt pin 224a, which brings it to a logic high level (a digital “one”). Theresulting interrupt triggers the execution of an interrupt handler. Theinterrupt handler is immediately able to determine that either the key212 a or 211 a was pressed, because they are the only two keys coupledto the first interrupt pin 224 a. However, the interrupt handler isfurther configured to scan the input pin 223 (which bears theuntransformed reference signal) and the interrupt pin 224 (which bearsthe transformed reference signal). Because the untransformed andtransformed reference signals differ from one another, the interrupthandler determines that the key pressed must belong to the second bank212. Hence, the interrupt handler correctly determines that the key 212a was pressed. Were the key 211 a to have been pressed instead, a scanof the input pin 223 and the first interrupt pin 224 a would revealsubstantially the same (i.e. untransformed) reference signal, allowingit to determine correctly that the key 211 a had been pressed. The sameexample applies to the remaining keys 211 b, 211 c, 211 d, 211 e, 211 f,212 b, 212 c, 212 d, 212 e, 212 f and interrupt pins 224 b, 224 c, 224d, 224 e, 224 f.

FIG. 3 is a flow diagram of one embodiment of a method of receivingsignals from a keypad. The method begins in a start step 310. In a step320, one of an untransformed and a transformed time-varying referencesignal are provided to an input pin of a processor. In a step 330, theuntransformed reference signal is provided to an interrupt pin of theprocessor when a key in a first bank is pressed. In a step 340, thetransformed reference signal is provided to the interrupt pin when a keyin a second bank is pressed. In a step 350 and in response to assertionof an interrupt on the interrupt pin, the states of the input andinterrupt pins are compared to determine which of the key in the firstbank and the key in the second bank asserted the interrupt. The methodends in an end step 360.

At least a portion of the above-described apparatuses and methods may beembodied in or performed by various conventional digital dataprocessors, microprocessors or computing devices, wherein these devicesare programmed or store executable programs of sequences of softwareinstructions to perform one or more of the steps of the methods, e.g.,steps of the method of FIG. 3. The software instructions of suchprograms may be encoded in machine-executable form on conventionaldigital data storage media that is non-transitory, e.g., magnetic oroptical disks, random-access memory (RAM), magnetic hard disks, flashmemories, and/or read-only memory (ROM), to enable various types ofdigital data processors or computing devices to perform one, multiple orall of the steps of one or more of the above-described methods, e.g.,one or more of the steps of the method of FIG. 3. Additionally, anapparatus, such as an HVAC controller, may be designed to include thenecessary circuitry or programming to perform each step of a method ofdisclosed herein.

Portions of disclosed embodiments may relate to computer storageproducts with a non-transitory computer-readable medium that haveprogram code thereon for performing various computer-implementedoperations that embody a part of an apparatus, system, or carry out thesteps of a method set forth herein. Non-transitory used herein refers toall computer-readable media except for transitory, propagating signals.Examples of non-transitory computer-readable media include, but are notlimited to: magnetic media such as hard disks, floppy disks, andmagnetic tape; optical media such as CD-ROM disks; magneto-optical mediasuch as floptical disks; and hardware devices that are speciallyconfigured to store and execute program code, such as ROM and RAMdevices. Examples of program code include both machine code, such asproduced by a compiler, and files containing higher level code that maybe executed by the computer using an interpreter.

Those skilled in the art to which this application relates willappreciate that other and further additions, deletions, substitutionsand modifications may be made to the described embodiments.

What is claimed is:
 1. An HVAC controller, comprising: a keypad havingat least a first bank and a second bank; a processor having interruptpins coupled to corresponding keys of both the first bank and the secondbank and a further interrupt pin coupled to an output of atransformation circuitry to receive one of an untransformed referencesignal and a transformed reference signal; wherein the processor isconfigured to: respond to an interrupt by determining whether a signalon at least one interrupt pin of the interrupt pins differs from asignal on the further interrupt pin; responsive to a positivedetermination, identify that a key in the second bank asserted theinterrupt; and responsive to a negative determination, identify that akey in the first bank asserted the interrupt.
 2. The HVAC controller ofclaim 1, further comprising: a reference signal source configured togenerate the untransformed reference signal and provide theuntransformed reference signal to the first bank; and a transformationcircuitry configured to transform the untransformed reference signalinto the transformed reference signal and provide the transformedreference signal to the second bank.
 3. The HVAC controller of claim 2,wherein the transformation circuitry is configured to phase-shift theuntransformed reference signal to yield the transformed referencesignal.
 4. The HVAC controller of claim 2, wherein the transformationcircuitry is configured to invert the untransformed reference signal toyield the transformed reference signal.
 5. The HVAC controller of claim1, wherein the untransformed reference signal is periodic.
 6. The HVACcontroller of claim 1, wherein the untransformed reference signal variesbetween volts and a digital logic voltage.
 7. The HVAC controller ofclaim 1, wherein the untransformed reference signal is a square wave. 8.A method of receiving signals from a keypad, comprising: providing, by atransformation circuit, one of an untransformed and a transformedtime-varying reference signal to an input pin of a processor; providingthe untransformed reference signal to an interrupt pin of the processorwhen a key in a first bank is pressed; providing the transformedreference signal to the interrupt pin when a key in a second bank ispressed; determining whether a signal on the interrupt pin differs froma signal on the input pin; responsive to a positive determination,identify that a key in the second bank asserted the interrupt; andresponsive to a negative determination, identify that a key in the firstbank asserted the interrupt.
 9. The method of claim 8, wherein the inputpin of the processor is coupled to an output of the transformationcircuit.
 10. The method of claim 8 further comprising phase-shifting theuntransformed reference signal to yield the transformed referencesignal.
 11. The method of claim 8 further comprising inverting theuntransformed reference signal to yield the transformed referencesignal.
 12. The method of claim 8, wherein the untransformed referencesignal is periodic.
 13. The method of claim 8, wherein the untransformedreference signal varies between zero volts and a digital logic voltage.14. The method of claim 8, wherein the untransformed reference signal isa square wave.
 15. An HVAC system, comprising: a controller associatedwith at least one of a compressor, a furnace, and a blower, thecontroller comprising: a keypad having at least first and second banks;a processor having interrupt pins coupled to corresponding keys of boththe first bank and the second bank and a further interrupt pin coupledto an output of a transformation circuitry to receive one of anuntransformed and transformed reference signal; wherein the processor isfurther configured to: respond to an interrupt by determining whether asignal on at least one interrupt pin of the interrupt pins differs froma signal on the further interrupt pin; responsive to a positivedetermination, identify that a key in the second bank asserted theinterrupt; and responsive to a negative determination, identify that akey in the first bank asserted the interrupt.
 16. The HVAC system ofclaim 15, wherein the controller further comprises: a reference signalsource configured to generate the untransformed reference signal andprovide the untransformed reference signal to the first bank; and atransformation circuitry configured to transform the untransformedreference signal into the transformed reference signal and provide thetransformed reference signal to the second bank.
 17. The HVAC system ofclaim 16, wherein the transformation circuitry is configured tophase-shift the untransformed reference signal to yield the transformedreference signal.
 18. The HVAC system of claim 16, wherein thetransformation circuitry is configured to invert the untransformedreference signal to yield the transformed reference signal.
 19. The HVACsystem of claim 16, wherein the untransformed reference signal isperiodic and a square wave.
 20. The HVAC system of claim 16, wherein theuntransformed reference signal varies between zero volts and a digitallogic voltage.